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Author | Topic: Human Brain Evolution Was a 'Special Event' | |||||||||||||||||||
RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
(1) The 20 to 25 million years is based on the divergence of the human lineage from that of the macaque, and does not say when in that period the mutations occurred. Similar studies show much more brain mutation\selection in the human lineage than in the chimp lineage, cutting the time period down to 6 to 7 million years, except that we don't know the base values for macaque to chimp and how much more mutation\selection is evident in chimps vs macaques.
My feeling is that including chimps would show a higher rate and (but not all) of the mutations\selection occurred since {chimp\human} split. My reason for this feeling is both the major change in brain size in Homo sapiens (as noted in the article) and because: (2) Sexual selection operates on every mating\generation. This means that any mechanism that employs sexual selection will consistently show a higher rate of selection than one that only employs survival. Survival is only tested in bad times, so it does not provide and selection pressure in good times (beyond basic viability). The human brain shows signs of classical Fisherian run-away sexual selection (from the article linked in OP):
quote: So large it endangers the life of the mother at birth. So large it can't get larger (unless all births are by C-section and we 'evolve' a new technique for birth to avoid this problem). (3) rates of mutation and "genetic clocks" are basically post hoc ergo propter hoc calculations rather than predictive in values. I have trouble with "genetic clock" type inferences that seem to fall back into old stereotypical gradualism models of evolution that ignore (a) differential rates of selection beteen sexual and survival and (b) ignore periods of intense survival selection that can cause punk-eek type evolution rate changes. Example again from the article:
quote: They only consider the average rates within each period. There could easily be a range of rates that depend more on selection pressure acting on the populations than on the rates of mutation, so what you are seeing is not a change in rates of mutation, but an increased selection for change instead of for stasis. Until some studies are done to delineate the actual maximum (minimum = 0) rates of changes possible and compare those to actual selection mechanisms and mutation rates, the whole concept of {faster\slower} is ill-defined and sloppy thinking. In my, of course, humble (but sometimes arrogant) opinion ... (imochbsao?) (4) the selection is for is not necessarily 'intelligence' in spite of what the article says:
quote: I think this is more human hubris than fact. We like to think we are so much smarter than any other animal eh? Yet the range of human intelligence still overlaps the ranges in other animals. If the selection is sexual, driven by mating preferences rather than survival, then the critical elements are the ones that benefit mating: creativity, dance, song, etc -- and brain capacity for 'intelligence' is a by-product. For anecdotal evidence that this is so, just look at who is usually listed as the 'sexiest' (= most matable) people: actors, artists, dancers, rock stars, and NOT nobel prize winners. Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
... we know that the Australopithecus had about the brain size of a chimpanzee. But we don't know how much brain development separates Chimps and Macaques, so we can't claim it is all since we diverged from Chimps.
And why was suddenly brain size so important, ... Is it? The real question is "what is important that results in a large brain" eh? we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
It still is remarkable since the history of civilization is over a few thousand years or so, then have any mutations occurred throughout history that we have discovered? Have our brains grown bigger - are we still evolving? You are talking about the last 4-5k years when homo sapiens has been a species for ~160,000 years and has shown little development in brain size in that period (~3% of our species existence). The time since the start of brain development circa Australopithicus afarensis is ~3 million years. What you would notice in such a brief time is very very small incremental change if any. The other thing to consider is that the brain size may well be maxed out -- any larger and viable babies cannot be born from living mothers by natural means -- and it is only very very recently that C-sections have become an alternative to natural birth, so further increases lead to deaths of baby or mother. This forces further brain development to work inside the existing size limits by increasing the ability of the brain to process information. There is evidence that this too has been occurring, and could well STILL be occurring, as this gets around the size limitations, but you won't see it as readily as growth in brain size. There was another thread that discussed this in more detail ... Bones of Contentions. ... although it starts out a little differently (on racism). we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
If you look at the post with the {Peek} button (it will open another window) you can see how the coding was done.
Note -- it is usually considered bad form to link directly to images on other sites ("deep links") as it can cause high bandwidth use on those sites. There are some options for uploading images (mirroring them), but reference to the original site should also be provided. Admin can help with image hosting. (another wish-list item -- automatic conversion of all image links to be uploaded - like avatars - and linked to the original site) Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
There is no must for beneficial mutations to have occured during the time of civilization. And if there were any, they would not have to be increases in brain size. Also size is not necessarily 'beneficial':
The question on brain development in humans is WHAT is being selected. Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
So, a concentration of mutations in a few generations is not astounding, and may be seen as special if one chooses to see it that way. If mutations are random then the distribution of beneficial ones within the full spectrum will also be random.
chaos theory probably explains it It would be a good start. If selection operates on mutations beneficial to a certain direction then any random mutations in that direction will be selected when they occur - and will also be randomly distributed over time. The appearance of clumping is predicted by this mechanism. Even without discussing whether or not mutations happen at a steady rate, or the rate oscillates around a medium that reacts to change in the environment. Even without discussing WHAT the selection is for in human brain development. Enjoy. Edited by RAZD, : added second quote - hopefully got it right. when you edit you don't get the "message you are replying to" for reference anymore. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
... from neanderthals or another archaic homo group. Perhaps Homo erectus or Homo ergaster? http://www.dmanisi.org.ge/index.html
quote: They had basic stone tools, for whatever that is worth.
quote: Neander is not the only conclusion to reach here. Seems to be a romantic neo-european bias here ... Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Indeed, Pbo says, he will now search for the haplogroup D variant of microcephalin in his own studies of the Neandertal genome. That would be the test. We had a thread on mtDNA evidence for neander mix, that pretty well showed no mitochondrial mixing, but that did not rule out the possibility of male neander genes. Mammuthus was involved with the data IIRC. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Welcome to the fray Joman,
I think that what's amazing about the brain isn't it's size but it's cognitive abilities. Which is only a matter of quantity (not quality) compared to the cognitive ability of other apes or even other animals. A recent article talks about elephant self recognition as one of many examples of cognitive ability in other animals. Cognitive ability is related to connectedness as well as to size - of the surface area rather than volume (hence the convolutions).
So, when I see a cartoon of a naked man that lived 1oo,ooo years ago looking unsure about, whether or not, the rock in his hand might be a tool, I know that he didn't have the cognitive brain I have. So you base your understanding of ancient man on cartoons? Interesting.
It seems that brain size is supposed to be the great signature of the evolution of man. I suppose it's because it's the only remnant of the past that can be empirically measured which relates to the brain of man. Homo neanderthalus had larger brains than Homo sapiens, but were not able to compete with us (even with tools), and there are many other species with larger brains, therefore SIZE is NOT the "signature" you are looking for. A more accurate claim would be cognitive ability, which as you (correctly) note, is not necessarily associated with size. Even there, we see a gradation between all animals, with several species having individuals with cognitive ability that overlaps those of individual humans at the low end of the human spectrum. As for what remains as evidence in fossil skulls, it is not just the size of the skull but the size and distribution of different parts of the brain within the skulls as we transitioned from ape ancestor to homo sap, and this can also tell us details about the development of the "special" human brain. From Message 60:
As far as the genetics of brain size goes, it is not just a matter of size per se, but where that size increases in the intermediate forms. color yellow for empHASis. http://www.massey.ac.nz/~alock/hbook/brain.htm
quote:Note that specimen KNM-ER 1470 is in the above referenced chart as skull (F). continuing:
quote: So we don't just have brain SIZE for evidence, we also have relative areas and their development and change over time. KNM-ER 1470 is the "type" fossil for Homo rudolfensis, that lived about 1.8 million years ago and is skull (F) in the picture shown later in this post.
This is a unfortunate state of affairs for the theory of evolution since, the data being discussed (brain size) is so crude that it can't ever rise to the level of scientifically rational extrapolation...er something other than hot air. I love it when people confuse their misunderstanding of evolution with it being a problem for science. Evolution is the change in species over time, so when we see evidence for change in species over time, how is that a "problem" for evolution? And there is plenty of evidence FOR the change in species over time resulting in larger brain capacities in the lineage of human ancestry:(Source of this picture is 29 Evidences for Macroevolution: Part 1) The other data (quantity of mutations)only allows analysis of things as they are now. Except that we can compare the same data for closely related species - chimpanzees, bonobos, gorillas, etcetera, and see what elements were common and what are different.
What convinces me that the theory of evolution is falsified by these circumstances is my belief that man, can't survive, and couldn't have survived without cognitive ability enabling man to use fire, clothing and tools. So you are convince by your incredulity without any reference to facts or evidence? In addition to nwr's evidence in Message 59, we also have the record of Darwin in Tierra del Fuego quote: And certainly in Africa - where hominids evolved into Homo sap - there is not an issue of needing clothes or fire to keep warm. Apes also use tools and survive.
Without fire man can't cook, dry out nor keep warm. Man therefore, would've required adequate hair for survival. Your argument is based on your personal incredulity that this could have occurred. All you prove by this argument is your incredulity and your inability to imagine. We don't need to imagine clothes in Africa. We don't need to imagine fire to eat food without it, a practice still used in the world today (funny as it may seem).
But, if man once upon a time had adequate hair there wouldn've been any need for clothes and so, any evolution of hair loss would've been immediately selected back out of existence. When it comes to hair, what you are forgetting (or are ignorant of) is the force of sexual selection, and how it can select for a feature that may have less survival fitness, but gets passed on because it boosts reproductive success. Selection for a feature that threatens survival in those that best express it while at the same time showing evidence for increased selection in that direction is a signal of (Fisherian) runaway sexual selection. And selection continues to this day for humans to show less hair. If you are interested in more information on this issue go to Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution, especially Message 44 It is interesting to note that the shame associated with nakedness has no evolutionary rationale. And it is very interesting to note the total lack of shame in many native people that go naked day after day. All you are doing is projecting your personal (unnatural?) feeling onto others. The ladies in the (copyright) picture here: "a picture brought back from south africa to australia by my great grandfather in the early 1900s featuring two native girls " are neither shamed nor cold nor huddled around a fire.
I submit that the lack of these three things (fire,clothing,tools) can be proven to be life threatening. The facts above prove your hypothesis is false, but it is also false on several levels, not least of which is your assumption of all or nothing in these developments, while the evidence shows gradual developments in all those cultural features that benefited the ancestors that used them.
So, how did man survive until he obtained the benefit of cognitive thought? By ignoring your argument from incredulity and your straw man argument. The way animals in the world today survive in spite of your ignorance of evolution.
BTW...what came first the eye's of man or the holes in his skull in which they fit, and function? Please take this to a new topic (see Proposed New Topics) so we can discuss how Enjoy. quote boxes are easy we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
News article from Seattle Times - Nation & WOrld
Tuesday, November 28, 2006 - Page updated at 12:00 AM Humpbacks have unusual type of brain cells also found in humansquote: And evolved in other animals before humans even walked the earth? So - at least some of - the evolution of brain can be tied to communication. Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Humpback whales use tools? and clams got legs. lol. Perhaps they did the etching for the dolphins?
So "Long, and Thanks for All the Fish"
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
I think you got it:
Page not Found (404 Error)
quote: They do seem to be refering to whales with a list of tool abilities http://news.nationalgeographic.com/...607_dolphin_tools.html
quote: Using people to herd the remaining fish back to them? Humpback whales have brain cells also found i | EurekAlert!
quote: http://whale.wheelock.edu/archives/whalenet96/0044.html
quote: Knowledge of consequences as well eh? we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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